The invention concerns a steering system of a vehicle, especially of a motor vehicle.
Vehicle steering systems, as is known, comprise a steering handle, especially a steering wheel, for manual actuation of the steering system. The steering wheel is coupled by a steering column to at least one steerable vehicle wheel, and by turning the steering column about a steering system axis this at least one vehicle wheel can be steered, i.e., its toe angle can be adjusted.
Motor vehicle steering systems are already known from the prior art in which the steering wheel can be adjusted in the axial direction and/or transversely to the axial direction. In this way, comfort functions are provided, for example making it easier to get into and out of the vehicle, as well as enabling an adaptation of the steering wheel position to the body height of the driver.
By the term “highly automated driving” is meant initiatives in the automotive industry for handing over the control and thus, in particular also the steering, of the motor vehicle, in the manner of an autopilot to an electronic controlling and computing unit (so-called onboard computer) so that the driver no longer needs to perform any driving tasks (or at least not continually) and can devote himself (temporarily) to other activities.
However, it turns out that the steering wheel rotation during the automatic actuation of the steering system in the highly automated driving mode is perceived as annoying by the driver and, furthermore, unintentional steering interventions by the driver can occur.
Therefore, it is an object of the invention to create a vehicle steering system which enhances the comfort for the driver during highly automated driving and prevents unintentional manual steering interventions of the driver.
This and other objects are achieved according to the invention by a steering system for a motor vehicle, with a steering handle for the manual actuation of the steering system, at least one steerable motor vehicle wheel which can be mechanically coupled to the steering handle, a steering column which is rotatable about a steering system axis and has an input shaft connected fixedly to the steering handle and an output shaft which can be coupled to the input shaft and whose rotary movement produces a steering movement of the steerable vehicle wheel via a steering gearbox, as well as a steering system blocking element, which is connected fixedly to a body of the motor vehicle. A locking device is provided which can optionally enable or block a relative rotation between the input shaft and the body-mounted steering system blocking element. A coupling device is provided, which can optionally enable or block a relative rotation between the input shaft and the output shaft. In this way, the input shaft, which is connected fixedly to the steering handle (no relative rotation between the input shaft and the steering handle) can be decoupled from the output shaft with little effort and fixed to the vehicle body during highly automated driving.
As a result of this decoupling of the steering handle from the at least one steerable motor vehicle wheel, unintentional manual steering interventions are effectively prevented. Moreover, the driver can use the steering wheel (=steering handle) locked to the vehicle body as a fixed support, for example, which contributes to enhanced driving comfort during the highly automated driving.
The locking device connected between the input shaft and the body-mounted steering system blocking element is, for example, a coupling, especially a jaw coupling.
In one possible embodiment of the steering system according to the invention, the steering handle is arranged so as to be axially movable for the actuation of the locking device. Such an actuating of the locking device is perceived by the driver as especially intuitive and thus likewise contributes to enhanced driving comfort.
It is preferably provided in this embodiment that the locking device in a first axial position of the steering handle enables a relative rotation between the input shaft and the body-mounted steering system blocking element and in a second axial position of the steering handle it blocks a relative rotation between the input shaft and the body-mounted component, wherein the steering handle in the second axial position has a shorter axial distance from the output shaft than in the first axial position. Thus, the steering handle when not in use (e.g., in its already mentioned function as a fixed support) is further away from the driver during the highly automated driving than in its actual function for manual steering system actuation. This larger axial spacing between the driver and the steering handle during highly automated driving also has a positive impact on driving comfort, since the driver enjoys more freedom of movement during highly automated driving.
Furthermore, a detent device can be provided, which axially fixes the steering handle in the first axial position and/or in the second axial position viewed in the axial direction (of the steering column). In this way, an unintentional actuation of the locking device can be reliably prevented with little expense.
The detent device is, for example, an electromagnetically actuated detent device and it can optionally enable or block an axial displacement of the steering handle. Through the electromagnetic actuation, it is possible to take into account parameter ranges of sensor data in which a switch between automatic and manual actuation of the steering system should be allowed or prevented, with little expense. Relevant sensor data might be, inter alia, the steering angle or the speed of the vehicle, so that during cornering and/or when driving at high speed no switch between automatic and manual actuation of the steering system is possible, for example.
Furthermore, a spring element can be provided, which forces the steering handle of the vehicle steering system into the first axial position. Thus, the spring element can move the steering handle (after giving a warning to the driver) from the second axial position into the first axial position, in which the driver must once more manually take over the vehicle control. This is advantageous, for example, if a redundancy function of the vehicle steering system fails during the highly automated driving, so that while the steering system is still functional, it no longer affords the required failure safety.
Preferably, the steering handle can be moved between its first and second axial position, wherein a dead center device can be provided, which assumes an unstable position of equilibrium between the first and second axial position of the steering handle and applies force to the steering handle in the direction of the first or second axial position outside of the unstable position of equilibrium. Thus, the dead center device ensures, in a simple manner, that the locking device is either in its enabled position or in its blocked position, but not in an unwanted intermediate position.
According to another embodiment of the motor vehicle steering system, the coupling device is a coupling, especially a jaw coupling, wherein the steering handle is arranged so as to be preferably axially movable for the actuation of the coupling device. Such an actuation of the coupling device is perceived by the driver to be especially intuitive and consequently contributes to enhanced driving comfort.
In particular, the coupling device in a first axial position of the steering handle can block a relative rotation between the input shaft and the output shaft, and in a second axial position of the steering handle it can enable a relative rotation between the input shaft and the output shaft. Especially in connection with an axial actuation of the locking device, this produces an especially simple switchover between manual and highly automated driving. By simple axial displacement of the steering handle, the steering handle can be decoupled from the output shaft of the steering column and fixed to the body-mounted steering system blocking element (highly automated driving) or coupled to the output shaft firmly against twisting and turned with respect to the body-mounted steering system blocking element (manual driving).
According to another embodiment of a vehicle steering system according to the invention, the coupling device can be designed in the manner of a superposition gear. This can include a drive unit for the electromagnetic actuation of the steering system, as well as a superposition ring, which can be coupled to both the output shaft and the input shaft and either be blocked by the drive unit or be turned about the steering system axis. The drive unit is designed in particular as a worm drive and can provide a steering angle setpoint directly for the steering gearbox during the highly automated driving so that a redundant drive unit is no longer needed in the steering gearbox itself. Alternatively, the superposition ring instead of the drive unit can be blocked by a blocking unit or its rotation about the steering system axis can be enabled. The blocking unit can be electromagnetically activated and accordingly enable or block a relative rotation between the input shaft and the output shaft depending on prescribed parameters.
The coupling device and the locking device are preferably mechanically or electrically/electronically coupled together in a steering system according to the invention so that the coupling device assumes its enabled position in a blocked position of the locking device, and vice versa. Thus, the vehicle steering system has only two defined shifted states, which are assigned to “manual driving” or “highly automated driving”. During manual driving, the locking device is in its enabled position and the coupling device is in its blocked position, while during highly automated driving the locking device is in its blocked position and the coupling device is in its enabled position.
Before explaining more closely the various features indicated thus far with the aid of possible figures represented in the enclosed figures (including further features and benefits of the invention), several other advantageous developments shall first of all be mentioned.
Thus, in a vehicle with a steering system according to the invention and a driver's seat adjustable by electric motor, the latter in the case of the second axial position of the steering handle, in which it has a shorter axial distance from the output shaft than in the first axial position, can be moved, actuated by an electronic control unit, into a position in which the driver's seat is also further away from the output shaft, viewed axially, than in the first mentioned axial position of the steering handle. In this way, the driver gets even more free space during the highly automated driving.
Moreover, it can be provided that an electronic control unit only enables an axial displacement of the steering handle toward the output shaft—whether initiated by the driver or initiated by an electromechanical servomechanism—when the vehicle can generally move in a highly automated driving mode or when the vehicle can be generally converted to the state of highly automated driving. The latter can be precluded especially during cornering and at relatively high speeds of travel. Moreover, such an electronic control unit can automatically initiate an axial displacement of the steering handle away from the output shaft (and thus toward the driver) when an error monitoring system for a highly automated driving mode of the vehicle identifies a safety-relevant error, which is why this state of the highly automated driver needs to be ended as quickly as possible. The corresponding returning of the steering handle to the driver can occur in this case electromechanically or, as already explained, by a suitable spring element.
Moreover, it can be provided that the steering handle in the second axial position (of highly automated driving) lies at least partially and at least approximately flush in a dashboard or the like of the vehicle at a shorter axial distance from the output shaft and then an indicator and/or operating unit for the driver is moved out of the dashboard into the direct visual field of the driver.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.